The object of this study is to describe the influence of body temperature on gas exchange and respiratory control in a representative cold-blooded vertebrate, the turtle. I have previously found that the relative ventilation (VE/VO2) of this animal decreases with temperature and that this is associated with an inverse relationship between the turtles blood pH and its body temperature. I now plan to extend these observations in several directions. Due to the relative hypoventilation at high temperature and the greater sensitivity to low inspired O2 at high temperature previously observed in my laboratory, I plan to focus on the effect of high temperature on gas exchange and O2 acquisition. I hypothesize that O2 supply may be a limiting factor at high temperature in these animals. I also plan to investigate respiratory control and blood acid-base status of turtles during rapid temperature change both in the whole body and in the brain alone. Finally, using the pronounced ventilatory responses to low inspired O2 and high CO2 I have observed as a basis, I plan to investigate the existence, location, and characteristics of chemical receptors involved in respiratory control and to do this at various temperatures.